Speaking of model numbers, AMD has apparently foregone a perfect opportunity to throw out its "clock speed equivalent" rating system that's increasingly less relevant over time especially now that dual cores are here. Take the Athlon 64 X2 4800+, for example. The 4800+ is literally a pair of K8 cores running at the same clock speed as a single Athlon 64 4000+, but it only gets a model number increment of 800. Too modest? Perhaps, but who's to say? Clock speeds aren't a faithful indicator of CPU performance.
Most notably, the X2 doesn't share the Pentium D's relatively weak performance in single-threaded tasks according to 3D gaming benchmarks. The Athlon 64 X2 also consumes less power, at the system level, than the Pentium D 840 just a little bit at idle (even without Cool'n'Quiet) but over 100W under load.
In fact, the X2 frequently outperforms the Pentium Extreme Edition and Pentium D, which costs nearly twice as much(Pentium EE). Thanks to its dual-core config, the X2 also embarrasses some expensive single-core processors, like the Athlon 64 FX and the Pentium 4 Extreme Edition 3.7GHz.